The term "silicone oil" is used herein to designate water-insoluble silicone polymers which are applied to hair to improve its feel or appearance. Silicone oils can provide the hair with a silky, lubricious feel. They can also provide a lusterization effect. These results are obtained by coating hair strands with thin films of silicone oil. Since silicone oils are substantially water-insoluble, after application to the hair they tend to remain thereon. Silicone oil can therefore be applied in a shampoo, or in a hair conditioner which is applied after shampooing and followed by water-rinsing.
The two most common types of hair conditioning silicone oils are referred to in the International Cosmetic Ingredient Dictionary (CTFA) as "dimethicone" and "dimethiconol". Dimethicone is defined as a mixture of fully methylated linear siloxane polymers end blocked with trimethylsiloxy units. Dimethiconol is a dimethyl silicone polymer terminated with hydroxyl groups. Such hair conditioning silicone oils are relatively non-volatile liquids, which are obtainable from commercial sources in the United States and other countries. For example, silicone fluids are sold by Dow Corning Corporation, Midland, Mich. Among the silicone oils (also called fluids) supplied by Dow Corning for use in hair treating compositions is a solution of high-viscosity dimethiconol fluid in dimethicone (Dow Corning Q2-1403 Fluid).
Since silicone oils have limited solubility in water and other polar solvents, they are usually applied in the form of dispersions or emulsions. For example, in a water-based shampoo or hair conditioner, the silicone oil may be dispersed with the aid of an emulsifying agent, and the dispersion or emulsion may be stabilized by the inclusion of thickeners.
Cationic hair conditioning agents are commonly used in hair conditioning compositions, and to a lesser extent in shampoo formulations. Typically, cationic hair conditioning agents contain one or more cationic quaternary nitrogen or amido amine groups, and one or more hydrophobic long chain aliphatic or silicone polymers. The cationic group can provide a degree of substantivity between the conditioning agent and hair. The long chain hydrophobic groups, which are derived from long chain fatty acids or are silicone polymers, can provide hair conditioning or hair repair functions.
The published European patent application 0 115 806 describes a hair conditioning composition containing silicone oil dispersed in water. The composition also contains dimethicone copolyol, which the Cosmetic Dictionary defines as a polymer of dimethylpolysiloxane with polyoxyethylene and/or polyoxypropylene side chains. To provide a stable emulsion, the composition is in the form of a gel vehicle, consisting of a lipid material and a cationic surfactant.
The incorporation of cationic hair conditioners in anionic surfactant-based shampoos presents a stability problem because of the tendency of the conditioner to interact with the surfactant. Anionic-cationic complexing of these ingredients can result in an unstable dispersion. The complexed conditioner/surfactant may settle out of the dispersion. However, some formulations have been developed in which quaternary nitrogen-containing conditioning agents are incorporated in anionic surfactant shampoos. U.S. Pat. Nos. 4,704,272, 3,964,500, and 5,034,218 are illustrative of such formulations. As described in these patents, the shampoo formulations may also include silicone oil which is dispersed and maintained in suspension by the inclusion of thickeners.
In the cited U.S. Pat. No. 4,704,272, a tri (long-chain) alkyl quaternary ammonium salt or a tri (long-chain) amine is utilized in combination with a synthetic anionic surfactant, a silicone oil, and a suspending or thickening agent. The patent disclosure indicates that the cationic conditioner does not interact with the anionic surfactant. Silicone oils are also used in after-shampoo hair conditioning emulsions. (See, for example, U.S. Pat. No. 4,387,090.)
As far as it is known, silicone polymers having an anionic functional group such as a phosphate have not heretofore been used commercially in hair conditioning compositions. However, methods of preparation and the chemical structure of phosphated silicone polymers are disclosed in U.S. Pat. No. 5,070,171. The base polymer described in these patents contains a dimethylpolysiloxane chain with a side chain of polyoxyalkylene. This structure can be regarded as a co-polymer of a siloxane chain and a polyoxyalkylene chain.
This type of silicone co-polymers is designated by the CTFA as "dimethicone copolyol". The Cosmetic Dictionary definition is: a polymer of dimethylpolysiloxane with polyoxyethylene and/or polyoxypropylene side chains. Using that terminology, the phosphated silicone polymers of the above-cited patent can be called dimethicone copolyol phosphates. In terms of chemical structure, the phosphate group forms the terminus of the polyoxyalkylene side chain, and the end hydroxyl has been converted to an ester linkage to the phosphate group.
Hair conditioning lotions are conventionally formulated as aqueous solutions, dispersions or emulsions. Organic solvents are not ordinarily used as carriers for the hair treating agents. Organic liquids may be included in the total formula as emulsifiers or hair conditioners. For example, U.S. Pat. No. 4,493,824 describes a water-based hair rinse containing a minor amount of polyethylene glycol.